OPTIMAT BLADES Résumé de rapport

New Wisper standard load spectrum

Sixteen years back a load sequence for variable amplitude testing of materials in wind energy applications has been defined. The sequence has been synthesized from the measured flat wise blade root bending loads of 9 wind turbines varying from18 kW to 3 MW in power and from 12 m to 100 m in diameter. Very different operating philosophies have been covered. This load sequence called WISPER has found international acceptance and is widely used in variable amplitude testing of wind turbine rotor blade materials. In the context of the OPTIMAT BLADES project that aims at optimising materials and design recommendations for wind turbine rotor blade it has been proposed to set up a NEW WISPER standard load sequence that reflects todays state-of-the-art in wind energy conversion technology. The idea is that material characteristics like fatigue life limits can be provided with better confidence for use in modern wind turbine rotor blade design when a test sequence reflecting todays turbine technology is used to establish such characteristics.

Following this line of thinking a work group within the OPTIMAT BLADES project has been formed to work out a NEW WISPER standard load sequence. The work group consisting of CRES, ECN, DEWI, DLR and WMC represents considerable experience in the field of wind turbine load determination and material testing. The reports present the major issues that have been discussed when creating NEW WISPER. The final resulting NEW WISPER sequence is presented and compared to the old WISPER standard sequence. The comparison is carried out on the basis of the rain flow range pair load spectra, 1-Hz equivalent load calculations and even more complex damage calculations using GFRP-material Goodman-diagrams and advanced damage accumulation models.